EGP Gateway under Berkeley UNIX 4.2
RFC 911

Document Type RFC - Unknown (August 1984; No errata)
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Network Working Group
Request for Comments: 911

                      EGP GATEWAY UNDER BERKELEY UNIX 4.2

                                  PAUL KIRTON

       University of Southern California, Information Sciences Institute
     Visiting Research Fellow from Telecom Australia Research Laboratories

                                22 August 1984

                                   ABSTRACT

This  report  describes an implementation of the Exterior Gateway Protocol that
runs under the Unix 4.2 BSD operating system.  Some  issues  related  to  local
network configurations are also discussed.

Status of this Memo:

This  memo describes  an implementation of the Exterior Gateway Protocol  (EGP)
(in that sense it is a status report).  The memo also discusses  some  possible
extentions  and  some  design  issues   (in that sense it is an invitation  for
further discussion).  Distribution of this memo is unlimited.

    Funding for this research was provided by DARPA and Telecom Australia.


RFC 911                                                                       i

                               Table of Contents

1. INTRODUCTION                                                               1

1.1 Motivation for Development                                                1
1.2 Overview of EGP                                                           2

2. GATEWAY DESIGN                                                             4

2.1 Routing Tables                                                            4
     2.1.1 Incoming Updates                                                   5
     2.1.2 Outgoing Updates                                                   5
2.2 Neighbor Acquisition                                                      6
2.3 Hello and Poll Intervals                                                  6
2.4 Neighbor Cease                                                            7
2.5 Neighbor Reachability                                                     7
2.6 Sequence Numbers                                                          8
2.7 Treatment of Excess Commands                                              8
2.8 Inappropriate Messages                                                    8
2.9 Default Gateway                                                           9

3. TESTING                                                                   10

4. FUTURE ENHANCEMENTS                                                       11

4.1 Multiple Autonomous Systems                                              11
4.2 Interface Monitoring                                                     11
4.3 Network Level Status Information                                         11
4.4 Interior Gateway Protocol Interface                                      12

5. TOPOLOGY ISSUES                                                           13

5.1 Topology Restrictions and Routing Loops                                  13
     5.1.1 Background                                                        13
     5.1.2 Current Policy                                                    14
5.2 Present ISI Configuration                                                15
     5.2.1 EGP Across ARPANET                                                17
     5.2.2 EGP Across ISI-NET                                                17
     5.2.3 Potential Routing Loop                                            18
5.3 Possible Future Configuration                                            18
     5.3.1 Gateway to UCI-ICS                                                18
     5.3.2 Dynamic Switch to Backup Gateway                                  19
          5.3.2.1 Usual Operation                                            19
          5.3.2.2 Host Initialization                                        19
          5.3.2.3 When Both the Primary and Backup are Down                  20
          5.3.2.4 Unix 4.2 BSD                                               20

6. ACKNOWLEDGEMENT                                                           21

7. REFERENCES                                                                22


RFC 911                                                                       1

1. INTRODUCTION

The Exterior Gateway Protocol (EGP) [Rosen 82; Seamonson & Rosen 84; Mills 84a]
has been specified to allow autonomous development of different gateway systems
while  still  maintaining  global distribution of internet routing information.
EGP provides a means for  different  autonomous  gateway  systems  to  exchange
information about the networks that are reachable via them.

This  report  mainly  describes  an  implementation  of EGP that runs as a user
                               *                                  **
process under the Berkeley Unix  4.2 operating system run on a VAX    computer.
Some  related issues concerning local autonomous system configurations are also
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